Process for improving the permeabilityramming characteristics of foundry sand



July 31, 1956 w. H. MOORE PROCESS FOR IMPROVING THE PERMEABILITY-RA 'fMING CHARACTERISTICS OF FOUNDRY SAND 4 Sheets-Sheet 1 Filed Sept. 19, 1952 f/DEAL SAND 4 5 6 7 8 NUMBER OF RAMS LESS IDEAL COND/ T/ON NUMBER OF RAMS IN V EN TOR. W/L LIAM H. MOORE BYMQMZQZ 1 M j' July 31, 1956 W. PROCESS FOR IMPROVING THE PERMEABILITY-RAMMIN Filed Sept. 19, 1952 H MOOR CHARACTERISTICS OF FOUNDRY SAND 1:1 .424. .iQNQ- NUMBER OF RAMS 4 Sheets-Sheet 2 IN VEN TOR.

WILLIAM H. MOORE W. H. MOORE July 31, 1956 2,756,476 PROCESS FOR IMPROVING THE PERMEABILITY-RAMMING CHARACTERISTICS OF FOUNDRY SAND 4 Sheets-Sheet 4 Filed Sept. 19, 1952 NATURAL BONDED SAND MOISTURE ITY 9L2 LITY 85.8

ILITY 82.3

NUMBER OF JOLTS INVENTOR. WILL/AM H. MOORE BY W, M M

United States Patent PROCESS FOR HVIPROVING THE PERMEABILITY- RAMMING CHARACTERISTICS OF FOUNDRY SAND William Henry Moore, Larchmont, N. Y., assignor to Meehanite Metal Corporation, a corporation of Tennessee Application September 19, 1952, Serial No. 310,438

8 Claims. (Cl. 22217) This invention relates to foundry practice in general, and relates more particularly to control of molding sand characteristics for making sand castings.

This application is a continuation-in-part of application, Serial No. 173,853, filed July 14, 1950, for Foundry Sand Control, now abandoned.

An object of this invention is to provide a method of controlling the variations in a sand which are due to the varying properties resulting when a sand is rammed to varying degrees.

Another object of this invention is to provide a method of controlling the uniformity of a mold produced by ramming, and the subsequent uniformity of surface finish produced on a casting.

Still another object of this invention is to relate the degree of change of said permeabilty and degree of change of strength to a theoretical ideal, and to one another.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which:

Figure 1 is a curve plotted from one given sand by testing the permeability over a variation in ramming;

Figure 2 is a dagrammatic representation of the reason why one given sand will pack more than another under ramming;

Figure 3 is a curve of several sands, plotted as in Figure 1, but each sand having difierent beginning and ending permeabilities at various levels;

Figure 4 is a graph of one sand plotting green compression strength variations in relationship to number of rams in a laboratory test sample;

Figure 5 is a graph of several sands plotted on the same coordinates as Figure 4, but each sand having different beginning and ending strengths, and each at a different level;

Figure 6 is a test mold, and the pattern for producing the mold;

Figure 7 is a graph plotting percentage of variation in mold hardness to percentage of ramability to illustrate the decrease in mold hardness variance with increase in ramability percentage;

Figure 8 is a graph showing vertical columns to illustrate the percentage of castings scrapped due to a defect, as compared to the percentage of ventability, with a dotted angular line illustrating the trend of decrease with increase of ventability percentage;

Figure 9 is a graph plotting percentage, ventability and bondability against moisture content in order to illus- "ice trate how these properties may be changed by varying the moisture content; and

Figure 10 is a graph showing the variation in mold hardness obtained in a test mold with different degrees of ramming and varying the values in ventability and bondability.

The preparation of a mold for casting metal has long been subject to many variables, particularly those variables due to uneven ramming or packing of the sand around the pattern. Thus in ramming by hand, for example, certain areas of the mold will always be rammed harder than other areas, and the resultant mold will not be uniform in its behavior towards the molten metal that is subsequently introduced into it. Where the ramming is soft, mold surface will be weak and porous, and the appearance of the casting at this point will be rough and uneven. When the ramming is hard the casting may contain defects due to the inability of the metal to lie quietly on a hard surface of high density.

The introduction of mechanical methods of ramming molds has done little to improve this situation, as the uniformity of ram is very largely dependent on the design of the mold cavity and the molding sand is unable to pack firmly in narrow pockets and the like. In the past, with a skillful hand ram it was possible to carefully pack the sand in these narrow pockets and thereby present a mold of fairly uniform properties. However, this peening operation requires more than average skill on the part of the operator and is time-consuming, so it has little place in the modern methods of manufacture.

This problem of obtaining a uniform mold surface by the ramming of sand has been given considerable attention in the past, but with little success. One such means has been to use a hardness tester on the molds in order to investigate the relative hardness at any particular spot in the mold. If this hardness was adjudged to be too low, then the ramming was increased. However, an increase in ramming increases the hardness at the spot under discussion and also increases the hardness at other portions of the mold. This method therefore does not improve the uniformity of hardness over the mold surface. The hardness can be raised and lowered by alteration in the degree of ramming, but the different hardness values in different areas of the mold cannot be substantially avoided by this means.

In order to make a commercially salable casting free from blemishes and defects, a mold surface must have two very definite properties at a suitable level. It must have strength and rigidity to resist the fluid pressure of the molten metal, and it must have permeability to dissipate steam and other gases. Too low a strength will lead to collapse of the mold surface and too high a strength may cause contraction strains and even cracks in the casting. Too high a permeability will give a rough, uneven surface to the casting, and too low a permeability will lead to blows, scabs and many other common casting defects.

It has been generally recognized that the permeability and the strength of a mold sand will vary according to the degree to which the sand is rammed, and according to the type and amount of bonding agent, as well as the amount of actual temper moisture present. Thus, as we ram harder we will increase the strength and decrease the permeability. It had not heretofore been realized, however, thattheamount of 'change inthese control in such a manner that a uniformly hard mold may be produced regardless of the degree and method of ram-.

ming employed.

The problem is to provide a mold of uniform permeability and of uniform strength across the whole surface. If this condition is present, it follows that a casting of uniform character can be produced. After considering this problem from many different standpoints, it was realized thatif a sand were of such a nature that it did not-{change im-permeability, or-in strength; as it was rammed from a relatively soft degree/of ram to arelatively hard degree of ram, it would'automatically give a uniform-moldirrespective of the method or degree-of ramming.

Laboratory measurements of permeability and' of strength-involvethe-preparation 'ofa standard sample 2 inches in diameter and 2 inches high. This sample is rammed-three times-by'dr'opping a weight of 14 pounds through a height: of 2 inches on the-sand; This 'is a standard' ram, .and it has long'been realized-that this standard degree of ramming used in the laboratory 'is not fully representative of the average degree of ramming used ina foundry. Each methodof ramming'in the foundry is either lesseror-greater than the standard ram, depending on whether theramming is a hand operation, a jolt operation, a jolt-squeeze operation, or aslinger operation.

As the result -of a long experience in the different methods of ramming and in the artof producing foundry moldsiand. cores, I have been ableto establish a ramming range 'in the laboratory manner which will adequately represent. the degree of ramming obtained with normal. methods of ramming used in production. Thus, if I r'arn a sandin the laboratory at one ram or one drop of the weight. as a'-. rninimum,-and 10 ramsor 10 drops-of the' intor der, to include...-.some unusual method of ramming in..,pra c tice,. I could.;also change the .l4.-pound weight used to. any. other ,value and :I could prepare the. samples by, diiferentmethodsoframmingu The standard method ofsampl e. preparation .has. been .chosen. as a basis ofmeasurement.merelybecause. of. convenience. In the sameway. ,the,range.of l to .10 rams onthestandard rammer has been. chosen merelybecause it is reasonably v representative and includes most. normal degreesof .ram

ming or hardness found in practice- My. testing methqd involves relating the. degree-of variance .ofpermeability and. of strength with variance in ramming, to an. ideal condition. An ideal condition .or'

an-ideal. sand is onewhich does not changeinpermeability, for in;strength over. thecomplete range ofyram-.

minglichosen fortesting purposes.

Reference..to..Figure 1 shows a graph which records the same level throughout the ramming range. ideal. sands are shown at different. levels of property values to'emphasize that the only requisiteofan ideal sand is no change in properties with ramming... It mat-. ters littlegwhether these properties .are at a high level or at a low level insofar as designatingthem as ideal. sands. Ideal simply means that .there would..be, no.

change in-permeability regardless of the number of .-rarns,.

One particular ideal sand may not be a suitable sand for a given mold although. it couldbe. If .theideal level falls at a strength that is too high or too low, or at a permeability level which is too high or too low, or both,

then a good casting will not result, regardless of the fact that the sand is an ideal sand and does not change its characteristics with additional ramming.

It should be emphasized that progressive ram tests are by no means new and have been conducted by many sand technicians in an effort to differentiate between the behavior of various sands. However, the tests are always at an arbitrary standard, not related to actual foundry practice. Further, and by far thegreatest failure, these tests stand alone as academic facts, unrelated in any way to-actual foundry practices; his a wellkr'iown"fact; until the time of -this'invention,-that laboratory 'testidata on sand are of little practical value, and that usually the-foundry foreman will alter, his sand I by-;some hunfc-hh or. guess,.;often based upon-.reasoning; amounting-.xalmost to superstition.

Thisinvention is based upon the fact illustrated graphically in'Figure 2, together with the selection and alteration of a foundry sandhaving ;a combination of permeability and strength factors related to one selected ideal sand, and to one another.

Figurei3 illustrates two facts which'were-heretofore apparent; but which were never used in'a process of selecting and blending a satisfactory mold'sand, as 'this' invention now teaches; Figure-3 is'a chart showing several curves resulting from'plotting-permeability changes" with respect to the number of-rams-in'a standard-com trolled laboratory test. In each case the permeability of .the sand decreases with increasing ramming-.- This fact*:is:expected,-and is explainable by the Figure'2. Bonding material and moisture are further factors affectingpermeability, but-inany event a given sand will produce' a test curve, or -any sand may be-compounded and alte'redto-produce a variety of curves.

From Figure 3, the fact is apparentthat not anydegreenfxpermeability can be obtained from one sand.- So'me sands;- however, give a much wider span of values, I resultingima graph more like Figure 1.

To be certain that the reason is understood for former failurexof laboratory sandtesting as a guide; let it be" assumed that thefoundry; technicianjknows. that a sand.- havinga permeability ofl30. (arbitrary scale) .is: satisn. factory for his job. This knowledge thata permeability". is satisfactory. is anempirical; knowledge. At the pres ent time,-. -there .is no certain .way to:predetermineziby i. scientific-means just what permeability is requiredfor any given, casting problem;

The technician then conducts a laboratory sandxitestx. consisting of'; three. rams 1 by a l4-pound weight 1. on; a standard.-- size sample. Assume ,thatthesandwhich was tested to produce the graph of .Figure .l wasithesi'oner; selected. The testgwould showthis sand to be-accept?- able...-;. Atthree rams, graph Figurel shows substantially} a permeability of 130.

But in:th'e .foundry this sand-would produce-many badcastingss. Theramming in the foundry is never uniform, regardlessof thetypetor-quali-ty of rammingrnachineavailable. Therefore, the mold maker may have ampletime-availableat one time of-the day, and he will'the'n give each mold a full measure of ramming. Iir'that' event the-actual mold permeability ofthe sand of Figure 1 will-be-considerably less than l30,-r naybe-; ES'IOWBS 60,"thereby producing a dense mold. The same"op'era-" tor, at another time, may be in a hurry' andram'onlyj enough to form the surface. This quick ram may then be only equivalent to a laboratory sample of one or two: rams. Figure .1 sand then would have a permeability of or 'or moreq Obviously, then, a standard ram test, sta nding.alone, will.rev,eal nothingof use-- fulness, .An .ideal sand. having a .permeability. .of..:l3'0

would solve the permeability problem, if such a sand were available. A

The first discovery of this invention, therefore, is the reason why standard permeability tests, standing alone, are of little or no value.

After this first discovery, one may conclude that the logical solution to the production of a desired permeability would be to control the ramming. But that solution is not satisfactory, especially in view of the human element involved. Adjustment of the average sand grain size and type, bonding material, and temper moisture, by additions to a sand, or the compounding of a new sand mix, for producing a sand more nearly like an ideal sand, is the better solution of the problem of permeability. But the more nearly a sand mix approaches an ideal condition, the less range of permeability it includes; therefore, the less universal in application it becomes. Accordingly, there is both a theoretical and practical limit in the approach toward an ideal sand.

Figure 4 is a study similar to Figure 1, taking into consideration the green compression strength of a sand with respect to the number of rams. Here the strength increases with increase in ramming. It is almost impossible to designate an ideal strength value, because of the many factors involved, but an ideal sand with respect to strength would be a sand which did not change in strength over a wide range of ramming, as shown by the straight broken lines of Figure 4. The Figure 5 shows a group of sands which have strength curves more nearly approaching ideal than the sand of Figure 1.

As explained above, an ideal sand which does not vary in properties as it is rammed progressively harder will give a mold of uniform properties in practice regardless of the degree of ramming used in practice. Such a sand would be 100 per cent with respect to freedom from permeability variance and with respect to freedom from strength variance.

For the sake of identification and ease of expression, the degree of variation in premeability with variation in ramming is called the ventability, and the degree of variation in strength with variation in ramming is called the bondability. On this method of nomeclature an ideal sand would have 100 per cent ventability and 100 per cent bondability. The terms ventability and bondability may be used by others, and if so are not to be given any general meaning in this field. Rather, these terms are intended to be limited strictly to the definitions just given.

From the foregoing discussion, it is apparent that the discoveries of sand behavior disclosed would be useful in reducing casting defects, if no further use were made of this information. However, if properly understood and applied, this information can be further utilized to perfect sand practice at the foundry level.

The foregoing discussion has disclosed the possible variations in sand behavior, and explained what an ideal sand would be. The actual sands produce a graph differing from the ideal sand. This difference can be related to the ideal, and a percentage value of the variation of permeability curves from the ideal of 100 per cent may be obtained.

By-the same token, the percentage value of the variation of the strength curves from the ideal of 100 per cent may be obtained.

The mechanics, or mathematics, of relating actual sands to ideal standards is explained hereafter. But it is the fact of relating that is believed to constitute the basic invention, not the specific mathematical method given. However, this specific method is new, inasmuch as it is part and parcel of the new basic discovery of said behavior, and its relationship to an idea.

We can now proceed to actually express and measure the ventability and the bondability of any molding or core sand simply by reference to an ideal sand. Con,- sider, for example, the test given in Figure 1. At the first ram the sand has a permeability of 216. If it had 166 I per cent ventability, it would show this same value of 210 over the complete ramming range. It now we set this ideal condition down in tabular form and divide each permeability value by the succeeding one we will have the following:

Where: P=pern1eability; R=ram number.

The same procedure may then be applied to the data in Figure 4. At the first ram a strength of 2.5 is shown. If this sand had per cent bondability, it would show .this same strength value at all rams over the test range.

The tabular relationship is as follows:

STRENGTH Strength Sub-Total Sat-R2 =E= SatRl 2.5

SatR3 SatR2 SatR4 SatR3 i SatR4 2.5

Where: S=strength; R=ram number.

In these ideal cases the total of the quotients equals 9.00 which would be equivalent to 100 percent ventability and 100 per cent bondability. It must be remembered that there is no significance in the value of 9.00 apart from the illustration given.

If now we set down in tabular form the actual results 7 obtained with .the.sand depicted weihaveftheizfollowingz in Figure 1 and Figure rannrnAnr-L irr V of Rams Permeability I v siub-Totali 2 100, F;.=%gg; 1.23

v 130 Z2Q= 1.22

3 62 231103- 11;;iiiiiiijjiiji:1:131:11: 533

' Total 15 Where: P -permeabihty;R=ram number. 7

STRENGTH N o. of Rams.v Strength. 1 Sub.-

Total 1 2.5 Z 1 5s" 2 3.9 gig-F 1.28

4 6.2 gzzgi=g= 1.16

5 7.2 gizgg=g+ 1.12

9 10.2 g fi 'ig 1.04

Total;'.; 10:64

Whe'rerS ='strength;-' R=ram number.

If we now substitute these totals formula:

Percent; ve-ntability orPbondability= 9.0(total9.0)

in the following percent ventability or bondability;(18.0total)X1111 81 r And the sand shown in Fi" re 4 will have:

percent bondability=(18.0 10.64) X 11.1 1-.

It has= now-been demonstratedhow thechangezinproperties with change in ramming of a sand may readily b related "to a theoretically ideal-condition: Tli 1nath= matics of this method are not ofi'mportance', for"on oer-i tainsands' it will be-found that the=changes'in -properties with ramming are an exact logarithmic-function and th'e='*- same=relationship to the ideal condition'maybe -expressedf-' by theme of logarithms. Also; as previouslycxplain'edg percent rammability =percent .ventability-l-percent bondability) =2 or this may be expressed in a singleformula thus:

The explanation of this method of evaluation has-beendealt-with in considerable detail motto. illustrate :ihev: mathematics of. relating sand properties: to an idealrconw dition, but merely to illustrate that the sand propertiesr:v may quite. easilybe-:related to our ideal condition. If now -wezagaini consider. the: .original :inventive thought, 1. that an. idealsand, froma property change -standpqint;;ir must giye. a moldofi'uniformproperties, irrespective .of's. thedegree. .andc-methodof -Iamming,;.we. cam-readily apr preciate ,the-basis of. this invention. 'I'he-same-inventivethought can be applied quite readily to any. other prop erty ofa molding sand which might vary with degreeor intensity of. rann- The properties: of peimeabality and .1 strength were chosen merelybcause :they have aqrelaa. tively: great. influence .on the. final casting producedufrommany.mold..

Having thus: shown how .the :rammabilityfiof asands: maybeaccuratelyevaluated, I am -in a betterlpositionto... demonstrate that these :functionswhichl have cal1ed..for.. convenienceventability, bondabilit y and rammability, have.:.

a tremendous influencecnthe qualityiof.castings produced. 4 in sand molds, and that by controlling these functionslto definite limits. I am. able to overcome.many of the prob? lemswhichhave'longbeen a source of difiiculty and ex-..-- pense to thefo'undry industry.

Practical useof this method of. evaluationand (control of thesepropertiesv described as rammingupropertiesl over a period of time has quite conclusively demonstrated their far-reaching .efictson' casting v quality and has aided very materially. in thecontr'ol of molding sandsi'j" use of the teaching given herein will resultin freedom from casting defects "heretofore. unknown; Defects 'du'e to :defective molds has long been the foundrymans'big gest problem. Therefore,v this invention" provides the solutionto'one of'the' m'ost baflii'ngproblems: Actual experience in using the principles of this inventio'niover." considerable time? of experimentation and study? has. proventhe principles given *to" be sound, *and' of inestimable value. 7

The scope of -this 1 method of 'sandcontrol may readily be "appreciated from the following examples 1" Uniformity of molds-- The effect of r'ammability on mold uniformity may. be'. seen clearly in Figures 6 and 7. Figure .7'is-aplotted curve of a sand showing the relationship of variation of hardness. of various sands rammed in the mold ofFi gure 6 withi'respect to percent of rammability. A test mold is.

depicted. in Figure .6 which was rammed under standard.

conditions with the pattern having the dimensions shown. Hardness measurements were made on the face of the mold at points A, B, C and D. These measurements were averaged to give an average mold hardness for the complete mold, and the difference was taken between the highest reading and the lowest reading. The percentage variation of mold hardness was taken as the difference between the highest reading and the lowest reading divided by the average reading times 100.

A mold was rammed from different sands having different values of rammability.

The graph shows definitely that as the rammability approaches the ideal condition of 100 percent rammability, the variation in mold hardness is materially reduced. Thus we can readily control mold hardness variation by controlling the rammability of the sand used for making the mold.

The uniformity of surface finish on the castings improved directly With the improvement in ramability.

Decrease in casting defects The ram properties can be used in reducing and elimination of defects due to sand. This is illustrated quite clearly in Figure 8, which shows the relationship between ventability and percent of castings scrapped due to scab defects. This graph was plotted from results over several months of operation in a foundry making a particular casting under controlled conditions, but Where the ram properties were not under control. Subsequent control of the ventability to desirable limits eliminated these costly scab defects.

Improvement in casting surface finish The ram properties can be used in the improvement of casting surface finish. It follows that if the molds can be made uniform by means of these properties, a uniform surface finish will result on all areas of a casting. By selecting a sand having sufficient smoothness to give a good surface and then making this sand having high ventability and bondability, it is possible to reproduce this smooth surface in the casting under a wide range of ramming conditions.

Ramming of molds It has been shown that increasing uniformity of mold properties may be obtained by having the sand at a suitably high ventability and bondability value. It follows, therefore, that for any fixed method of ramming, the mold properties may be varied by changing the ventability and bondability. By the same token, the same uniformity of mold properties may be obtained in two cases in the following manner:

In case 1, the sand has a low ventability and bondability and the ramming is made excessively hard in order to overcome the natural reluctance of the sand to conform the ideal condition.

In case 2, the ventability and bondability are high and a lesser degree of ramming is necessary to make this sand conform to the ideal condition. By increasing ventability and bondability, therefore, a mold of uniform properties may be obtained with a lower degree of ramming. We have, therefore, an excellent means of decreasing the power, energy and time necessary to make a mold of given uniformity. This, of course, leads to increased production and decreased molding costs. This concept is illustrated in Figure 10 showing the variation in hardness values obtained with a test casting.

Reference to Figure 10 shows that for the same percentage of variation in mold hardness, for example 30, the ramming degree used is less in the case of the sand having the highest ram properties. This means that by increasing the rammability of the sand mix used, it is possible to maintain an acceptable mold uniformity using a lesser ramming force. By doing this, great economies 10 in molding time and increase in production may be obtained.

It has been established by the disclosure given that every sand exhibits a degree of permeability change and a degree of strength change with variation in degree of ramming. These degrees of change are measurable and have been called the ventability and the bondability respectively. The combination of both the permeability change and the strength change has been called the rammability.

It has also been shown that these properties designated ventability, bondability and rammability may be used to increase mold uniformity and decrease casting defects. Anyone skilled in the foundry art knows that certain permeability values and certain strength values in their sand normally give them suitable castings. This knowledge is purely empirical and is based on years of bitter experience usually by trial and error. The reason that it is so difiicult to establish a definite value of strength or permeability that will give an acceptable casting is because the strength and permeability that we actually obtain in a mold is not necessarily the same as that which we obtain in a laboratory test.

My invention enables us for the first time to translate laboratory test values of permeability and strength directly to the mold. This is done because under my invention we compound a sand mixture which does not vary in properties as the degree of ramming is varied. Consequently, we are able to eliminate the degree of ramming variable. This has never been done before.

In this particular invention, we are interested in pro viding a sand that will give us a uniform permeability and uniform strength in any mold that is made from the sand, irrespective of the method used in making the mold. We must assume that anyone skilled in the art will select a sand that will give a good level of properties in the mold calculated to give a good casting.

It now remains to be shown by specific example that the properties of ventability, bondability and rammability are capable of finite control. They may be varied by anyone skilled in the art to give the desired values necessary for the production of any particular casting or mold.

It was illustrated in Figure 8 that a lower defective loss due to scabs resulted when the ventability was higher. If in this case the economically accepted defective loss on these castings was 2%, it is obvious that a ventability above 86% is necessary in the manufacture of these castings.

The inclusion of ventability in the castings discussed in Figure 8 was necessary because conventional sand properties such as permeability and strength failed to show any means of reducing the high defective loss I This is because the test values of permeability and strength obtained in the sand used was not translated to the mold.

In other words, no provision was made for the variation in properties of the sand as the degree of ramming varied. By allowing for this variation in properties with degree of ramming in the form of a ventability measurement, it was found thatthe actual molds could be made to give serviceable castings.

If now, the sand in this particular case is found to have a ventability of 82% with consequent higher than allowable defective loss, the problem is to increase the ventability of-the sand to the acceptable 86% figure.

- This sand could be corrected in a series of steps, thus:

STEP 1 deliberately changing the distribution, therefore, the

ventability may be altered as desired. By way of exwould proceed I with Step 3.;

ample, a sand mixture havingthe following grain analysis gave?"vt'entability of82.5%. I

It' should' be noted th'at 8720% of the grai'ns are 'on four adjacent screensn By ch'angingQ- thEdistribution to give-' approximately the'- san1e '-=percentage oli 'grain's on--- thfee' adjacent -screens-a ventability "of 84.6% resulted',= thfi SZi v Percent 20?. mesh 0.2; mesh 0.121' 40.t.mesh 0.5] or SOZmesh 25.9 70'fm t 3863 86.4 IOOZ'Lmesh'Q 22.2 14'0 'fmesh.- 3.0 200'.'me'sh; 0.4; 9 Pan I 2.1 Clay and vsilt" 7.3 f' Ventability 8416 T In the-ispecifio example quoted the changezin grainfidisfi tributioniwoulclhnotbefisuflicientto :give the desiredsvent r 3 5 abilityts In=:such a case We would proceed1with1Step v2. 5

STEP 2 1 Examine the clay content of. thersa'nd mixture and reduceth'isiforfincreased ventability,

By way. of, example, the ventability ,ofsandi'mix was 40 foundfto be 84.3%; Thisimixflwas as follows Pounds' Heap san 800 11- New. -sand v ,160 Seat coal' 10- Fireclay 3072 The measured clay: content was 25.3 %1 by rthe-' hydromr-t eter methodirs The :mix was: changed 10:)" I

' Pounds 1 Hap sand 800 I New sand 1801 Sea coali 10ft Fireclay .I 10

They-measured clay :content of :thepnew mixwas 4.2% :9 andrthe ventability was 86.3%.- V

Ifz-SteprZ ,did1stillnotresult inzthe-rdesiredxchange We STEP- 3 V Examine "the moisture 'contentof the sand :andfredirce' this i for increased ventabilityg" This method of" control has been described in 'the"compani'on" -apjgllic'iation bearing t the .Sria'lTNo. U'.'. 5; 173,852 i'and entitledOpfimumfi TemperiMoisture Determination" in'Foundryg san" Irf' Figure-f9" the variation in bothventability a'nd bondabrhty withrnoisture content "ona typicalsand mix'is illustrated." By determining this data for thei sand mix under consideration, it becomes possible to select the moisture valu' that will give the *ventability; bo'ndabili't' y or ram 7 0 mability desired." I a p In addition tothe three stepsioutlined, there are Othi-'-"' means ofchangin'g the ventability bond'ability iiirarnriia bility to any"de'sired=valu'.-'- Th'ese means are tabulated as a general*diiective below and anyone skfl-ltl inlthe {art'-'- 12 will automatically select thebest course of procedure to follow'rather fhan -going through specific steps-as" outlined-F To raise ventabilit'yf v a: Usa finer grain as longas'the' resultant permeability will-fall wit'hih'the' desired limits;

c. Decrease thebondability. If this results in too low a-strengthfor normal operation, obtain 'fuller develop'- ment of availablebbndabilitybythe use of a small amount of Bentonit'eand by-increased mulling' d. Decrease the plasticity of the-bond;

T o raise-bondabih'ty':

rib-Use a lightly coarser grain.

'b. Use- "a more rounded grainP c. Decrease the amount ofbo'nd or'decrease the plasticity- "of the bond.

The opposite conditions will give the reverse of-thd effect anticipated and serve as 'dir'ectives forlowering'the ventability 'and the-bondabilityz' Although the invention has been described in its preferred form witha certain degree of particularity, it is understood-that the present disclosure of the 1 preferred for-m has-been made only by 'way of example-and that numerous changesin the details ofconstruction and'th'e combination and arrangement of parts may be resorted to without departingfrom the spirit and the scope--01? the inventionas hereinafter claimed.

Whatis claimedis:

l. A process *fo'r improving the permeability-ramming;- characteristics of a foundry" sand -"to 'obtain a predetermined permeability-change factor, said process comprising the steps of, providing a supply of foundry sand, test ramming and measuring the permeability-change between a firstandsemnd' degreebf ramming hardness-of an initial;:sample+portion' ofsaid sand,--physically altering" the permeability-ramming characteristics of said sand until .a subsequent sample=portionof altered sand shows" substantially said '5 predetermined permeability-change factor sbetweenwsaid same .first 'andsecond degrees of ramming hardness.

2..A processzzfor improving the perrn'eability-ramming characteristics of a foundry sand to obtain-a predeter mined permeability-change factor, said process comprising the steps of, providing a supply of'foundry sand, test ramming and measuring the permeability-changeibetween a first andsecond degree ot-ramming hardness-of"an*: initial-sample-portion of i said sand, physically: alteringfthe' permeability-ramming-characteristics of said sand '.-by:- changingethegrain sizedistribution of said sand'until a subsequent sample-portion'of'falteredssand shows substantiallysaid predetermined permeabilitywhange factor I between said same first and second degrees of ramming hardness. I v

3. A processfor-improving the permeability-ramming? characteristics: of: a foundry sand to obtain "a-predeter mined permeability-change factor, "said process compri's; ingthe' steps of; providing-- a supply of-foundry, sand,':testt ramming and measuringthe -permeability=changexbetween a first'and'second degree of ramming hardness-of an im'tializf' sample-portion of-isaid sand,-- physically alteringztthey permeability-ramming ch aracteristics of said sand by:- changing thebond-content ofsaid sand until "a subsequent sample-portion of altered sand shows substantially said "'1' predetermined permeability-change factor-- between said'r same first--and second degrees -of ramming hardness.

41 A process for improving the permeability-ramming characteristics: of --'-a' foundry sand to obtain: a predetermined permeability-change factor, said process compris ing-the steps of, "providin g a supply of 'found'ry sandfle-st rarrtirn'ing and measuring the permeability-change between 1 a first and second degree "of ramming -hardness 'of 'am initial 's'ample' portion of-s'aidSandQ physically alt'ei the-permeability ramming characteristics of f SHid' SZHd y changing the 'r'noisture'c'fontent (Sfsaid sand il'ntila su'bse' quent sample-portion of altered sand shows substantially said predetermined permeability-change factor between said same first and second degrees of ramming hardness.

5. A process for improving the strength-ramming characteristics of a foundry sand to obtain a predetermined strength-change factor said process comprising the steps of, providing a supply of foundry sand, test ramming and measuring the strength-change between a first and second degree of ramming hardness of an initial sample-portion of said sand, physically altering the strength-ramming characteristics of said sand until a subsequent sampleportion of altered sand shows substantially said predetermined strength-change factor between said same first and second degrees of ramming hardness.

6. A process for improving the strength-ramming characteristics of a foundry sand to obtain a predetermined strength-change factor said process comprising the steps of, providing a supply of foundry sand, test ramming and measuring the strength-change between a first and second degree of ramming hardness of an initial sample-portion of said sand, physically altering the strength-ramming characteristics of said sand by changing the grain size distribution of said sand until a subsequent sample-portion of altered sand shows substantially said predetermined strength-change factor between said same first and second degrees of ramming hardness.

7. A process for improving the strength-ramming characeteristics of a foundry sand to obtain a predetermined strength-change factor said process comprising the steps of, providing a supply of foundry sand, test ramming and measuring the strength-change between a first and second degree of ramming hardness of an initial sample-portion of said sand, physically altering the strength-ramming characteristics of said sand by changing the bond content of said sand until a subsequent sample-portion of altered sand shows substantially said predetermined strength-change factor between said same first and second degrees of ramming hardness.

8. A process for improving the strength-ramming characteristics of a foundry sand to obtain a predetermined strength-change factor, said process comprising the steps of, providing a supply of foundry sand, test ramming and measuring the strength-change between a first and second degree of ramming hardness of an initial sample-portion of said sand, physically altering the strength-ramming characteristics of said sand by changing the moisture content of said sand until a subsequent sample-portion of altered sand shows substantially said predetermined strength-change factor between said same first and second degrees of ramming hardness.

References Cited in the file of this patent Dietert: Foundry Core Practice, second edition, pages 424 129, published 1950. 

1. A PROCESS FOR IMPROVING THE PERMEABILITY-RAMMING CHARACTERISTICS OF A FOUNDRY SAND TO OBTAIN A PREDETERMINED PERMEABILITY-CHARGE FACTOR, SAID PROCESS COMPRISING THE STEPS OF, PROVIDING A SUPPLY OF FOUNDRY SAND, TEST RAMMING AND MEASURING THE PERMEABILITY-CHANGE BETWEEN A FIRST AND SECOND DEGREE OF RAMMING HARDNESS OF AN INITIAL SAMPLE-PORTION OF SAID SAND, PHYSICALLY ALTERING THE PERMEABILITY-RAMMING CHARACTERISTICS OF SAID SAND UNTIL A SUBSEQUENT SAMPLE-PORTION OF ALTERED SAND SHOWS SUBSTANTIALLY SAID PREDETERMINED PERMEABILITY-CHANGE FACTOR BETWEEN SAID SAME FIRST AND SECOND DEGREES OF RAMMING HARDNESS. 